Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2013 Interest Rate Swaps [Member] Swap	May 31, 2013 Interest Rate Swaps [Member] Swap	Aug. 23, 2012 Interest Rate Swaps [Member] Swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount interest rate swap			$ 550,000	$ 550,000	$ 550,000
Number of outstanding interest rate derivatives			2	2	2
Reclassified as an increase to interest expense		1,567
Tax on unrealized gain on derivatives	1,378	1,416
Termination value of derivatives in net asset position	$ 2,191	$ 2,191